Exploring carbon quantum dots as an aqueous electrolyte for energy storage devices

The facile accessibility of electroactive species to the surface of graphene-based supercapacitors is crucial. Here, we report the potential of carbon quantum dots (CQDs) as an electrolyte for graphene-based supercapacitors. The aqueous CQDs electrolyte properties are explored and compared with other commonly used aqueous electrolytes. A gravimetric capacitance of 155 F/g at a current density of 1 A/g is achieved with an aqueous 25 mM CQDs electrolyte having 0.43 S/cm ionic conductivity. The energy density of as-fabricated device is calculated to be ~55 Wh/kg at a power density of 3200 W/kg with a 1.6 V potential window (PW). Also, our approach comprises a solution-based flexible and free-standing CQDs-polymer gel (f-CPG) electrolyte film formation. The f-CPG film reveals an ionic conductivity of 0.48 S/cm and a high dielectric constant (972) with low dielectric loss (~12) at 2 MHz frequency at room temperature. The f-CPG electrolyte film exhibits a considerable electrochemical performance with gravimetric capacitance, energy, and power densities of 140 F/g, 50 Wh/kg, and 8534 W/kg at 2 A/g, respectively. The CQDs electrolyte could be an excellent choice for energy storage devices.